sizeof

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: Is there a more efficient way to load a large Mat object into memory than the FileStorage method in OpenCV? I have a large Mat with 192 columns and 1 million rows I want to store locally in a file and load into memory then my application starts. There is no problem using the FileStorage, but I was wondering if there exists a more efficient method to do this. At the moment it takes about 5 minutes to load the Mat into memory using the Debug mode in Visual Studio and around 3 minutes in the Release mode and the size of the data file is around

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: Quoting the code for computing the integer absolute value (abs) without branching from http://graphics.stanford.edu/~seander/bithacks.html : int v; // we want to find the absolute value of v unsigned int r; // the result goes here int const mask = v >> sizeof(int) * CHAR_BIT - 1; r = (v + mask) ^ mask; Patented variation: r = (v ^ mask) - mask; What is CHAR_BIT and how use it? 回答1: You should be aware that this code depends on the implementation-defined behavior of right bitshift on signed types. gcc promises to always give the sane behavior

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I'm trying to implement an replacement algorithm that deals with page faults. So i'm trying to creat a circular linked list using malloc and im getting the following error: "invalid application of sizeof' to incomplete type pageInMemory'.following is the code: typedef struct { int use; int reference; int free; struct pageInMemory* next; } pageInMemory; int main() { int i; struct pageInMemory* start, *nn, *temp, *hand; start = NULL; for(i=0; i< pNum; i++) { nn = (struct pageInMemory *)malloc(sizeof(struct pageInMemory)); nn->use = 0; nn->free

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I have a problem in my code. In Xcode or using the C++11 compiler, this code works well. However, when I am submitting this code to an Online Judge, the verdict shows "Compile Error" . I think they use the C++4.7.1 compiler, which when I tried to compile it (using Ideone), it says: prog.cpp: In function 'void printArray(int)': prog.cpp:27: error: 'void*' is not a pointer-to-object type prog.cpp:27: error: 'void*' is not a pointer-to-object type prog.cpp:27: error: 'void*' is not a pointer-to-object type prog.cpp:27: error: 'void*' is not a

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 由 翻译 强力驱动 问题: Imagine a structure like this: struct test_s { int i ; size_t namelen ; char name []; }; Now I would like to return an array of such structures to user code, also using a generic function which takes a void * pointer: size_t test_read ( void * buf , size_t bufsize ); Each of the array elements would need to aligned to struct s_s alignment. In each of array element the namelen is adjusted, so it is greater or equal then strlen(name) , but with additional "unused" bytes in between array members, so that next array member starts at

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I have a structure with no members (for the moment) and I would like to know if it is possible to suppress the warning I get: warning: struct has no members Is it possible to add a member and keep the sizeof the struct zero? Any other solution? 回答1: In c the behaviour of an empty structure is compiler dependent versus c++ where it is part of the spec ( explanations here ) C++ A class with an empty sequence of members and base class objects is an empty class. Complete objects and member subobjects of an empty class type shall have nonzero

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 由 翻译 强力驱动 问题: I'm trying to understand the usefulness of static_assert , and I want to know if it can help me in enforcing a design, and if so, how. I have a general template class that hides its own implementation inside another template class which is partially specialized based on the size of the template type. Here's a brief outline of this design: template < class T , size_t S = sizeof ( T )> struct Helper ; template < class T > struct Helper < T , sizeof ( long )> { static T bar (); }; // ... other specializations ... template < class T >

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I currently have some code that sets up notifications of connected USB HID devices within a Windows Service (written in C++). The code is as follows: GUID hidGuid; HidD_GetHidGuid(&hidGuid); DEV_BROADCAST_DEVICEINTERFACE NotificationFilter; ZeroMemory(&NotificationFilter, sizeof(NotificationFilter)); NotificationFilter.dbcc_size = sizeof(DEV_BROADCAST_DEVICEINTERFACE); NotificationFilter.dbcc_devicetype = DBT_DEVTYP_DEVICEINTERFACE; NotificationFilter.dbcc_classguid = hidGuid; HDEVNOTIFY deviceNotify = RegisterDeviceNotification(StatusHandle

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 由 翻译 强力驱动 问题: Suppose I declare int v[]={1,2,3,4,5}; I have been taught that v is a pointer to the first element in the v array. When I call apply sizeof to v , it returns 20, which I know is 5*sizeof(int) , because there are 5 elements in the array. v+0 is also a pointer to the first element in the array, but sizeof(v+0) is 4. Why is sizeof(v) =20 and sizeof(v+0) =4? I would expect that sizeof(v) also returned 4, as v is a pointer, but instead it somehow also contains the information regarding the number of elements stored in the array. What is

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 由 翻译 强力驱动 问题: I have a C++ question. I wrote the following class: class c { int f ( int x , int y ){ return x ; } }; the sizeof() of class c returns "1". I I really don't understand why it returns 1. Trying to understand better what is going on, I added another function: class c { int f ( int x , int y ){ return x ; } int g ( int x , int y ){ return x ; } }; Now the following really got me confused! sizeof(c) is still 1 (!?!?!?!). So I guess that functions doesn't change the size of the class, but why??? and why does the size is 1 ? And is it